P0128 – Coolant Thermostat (Coolant Temperature Below Thermostat Regulating Temperature) P0128 – Coolant Thermostat (Coolant Temperature Below Thermostat Regulating Temperature)

P0128 – Coolant Thermostat (Coolant Temperature Below Thermostat Regulating Temperature)
Description:                 Indicates the thermostat monitor has not achieved the required engine operating temperature within a specified amount of time after starting the engine.
Possible Causes:       
 
Insufficient warm up time
Low engine coolant level
 
Leaking or stuck open thermostat
 
Damaged engine coolant temperature (ECT) sensor
 
Damaged cylinder head temperature (CHT) sensor
Diagnostic Aids:          Refer to Section 1, Thermostat Monitor for system information.
Related Topics  P0113 - Intake Air Temperature (IAT) Sensor 1 Circuit High

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